Clamps of the above mentioned type are used in conveyors of articles, for instance in belt or chain conveyors, for supporting components thereof, such as guides for the containment/routing of the transported articles.
In such applications, the clamps normally sustain a respective bar (for example a steel rod) intended in turn to support guide-holding elements of the guide for the containment/routing of the articles. The bar has, mounted on one end thereof (also referred to as the head), a guide-holding element, and the bar is clamped by the clamp, with the possibility of adjusting the bar position, the clamp being in turn fixed to the frame of the conveyor.
The conveyors of articles are often used for transporting articles of various shape and size, so that it is necessary to be able to adjust the position of the containment/routing guides, depending on the type of articles to be transported (for instance, plastic bottles for drinks of various size).
A known clamp of the above-mentioned type is shown for instance in the Italian utility model application No. MI99U000397. Such a clamp includes an external body for the operations of positioning and adjusting of the protruding bar section (“pivot”), on which the guide-holding element is mounted. Such external body consists of a hollow cylindrical body having a coaxial pair of through holes (adapted in use to be traversed by the bar) formed in its side wall and close to an upper end thereof, and has an inner diameter that reduces in proximity of a step. A movable member, movable inside the hollow cylindrical body along the longitudinal axis thereof, is urged by a helical spring interposed between the step and the movable body. A handle grip is snap-mounted on an upper appendix of the movable member so as to be rotatable relative to the movable body without substantially moving axially with respect thereto. Particularly, the handle grip has a pair of blades (“plug pins”) that, in use, are respectively accommodated in a pair of shaped guide openings formed in the upper part of the external body. In this way, when the handle grip is manually rotated by a user in the sense in which the plug pins are moved downwards into the openings, the movable member is pushed downward, against the action of the spring, until a through hole formed therein aligns with the pair of holes of the hollow cylindrical body, so as to allow the passage of the bar. Once the bar is inserted into the holes, by unscrewing the handle grip (and therefore bringing the plugs upward in the openings) the spring pushes the movable member upwards; an annular projection provided in the hole of the movable member can in this way engage one of the grooves provided in different longitudinal positions along the bar, selected in such a way that the guide-holding element mounted on the head of the bar takes the desired position along the belt conveyor. It is by means of such annular projection that the pushing action of the spring causes the clamping of the bar, necessary to keep the guides in the desired position.
The inventor has observed that such a clamp exhibits some drawbacks. In fact, a drawback of such solution is given by the fact that such a clamp is by its nature unsuitable to guarantee a suitable clamping of the bar, adapted to recover the inevitable plays existing between bar and the through holes in the clamp body, and therefore it does not assure that the articles containment/routing guides are kept in the desired position, as parallel as possible to the transport plane. In fact, the action exerted by the spring is not sufficient to prevent that the existing play between the bar and the edges of the through holes causes a displacement of the bar from the horizontal position. The bar, under its own weight and the weight of the guides mounted thereon, can in this way take an inclination (which is higher the longer the bar) that as a result causes an uncorrected alignment of the containment/routing guides. Such phenomenon is more penalizing in the case of conveyors that have several orders of superimposed, parallel guides: in this case, the inclination of the bars that support the guides can has the consequence that the distance between the axes of the upper guides is reduced, while that between the lower guides increases.
With the purpose of guaranteeing a tight clamping of the bar, it would be necessary to realize the spring in a material having very high elastic constant, so that the pushing action exerted by the spring on the movable body is very high. However, this would reduce the efficacy of the clamp under the viewpoint of the bar positioning easiness: a spring that exerts an excessive pushing action against the movable body would make it very difficult, not to say impossible, to longitudinally slide the bar so as to bring one of the grooves formed thereon in correspondence of the annular projection. In fact, in the mentioned clamp the longitudinal positioning of the bar relative to the axis of the hollow cylindrical body takes place simultaneously to the bar clamping, and always with the aid of the spring. In order to allow the sliding of the bar necessary to the positioning thereof, the action exerted by the spring necessarily has to be limited, and this jeopardizes the performances of the clamp in terms of bar clamping action. Thus, even if the force exerted by the spring is increased, this can never guarantee a stable blocking of the bar.
Moreover, the use of the mentioned clamp significantly impacts on the time necessary for the adjustment of the position of the containment/routing guides. In fact, when it is necessary to modify the position of the guides, for every clamp (in a typical transport line their number can be of several tens) the operator in charge of the conveyor set-up has to screw the handle grip up in order to release the bar, then slightly move the bar from its current position, subsequently unscrew the handle grip, checking that the guide-holding element mounted on the bar is brought into the desired position.
In view of the state of the art outlined above, the inventor has faced the problem of providing an improved clamp, that is not, or at least less affected by the above mentioned problems.